Helpful Resources

The cicadas are coming

By Sedonia Martin on May 19, 2017

One of nature's true spectacles, early emergers of Brood X have started to arrive
in Baltimore

Associate professor of biology John S. LaPolla, Ph.D. (Fisher College of Science & Mathematics) explained the emergence of the periodic cicadas now being seen on campus and throughout
the region. LaPolla did a feature interview with Catherine Hawley of WMAR-TV channel
2 in the Towson University insect lab on Thursday, May 18, which aired that night.

Why are we seeing cicadas now?

What are we seeing right now are the early emergers of Brood X. These are periodic
cicadas. This is a species that typically comes out every 17 years. So, the last time
this brood would have emerged was in 2004. What sometimes happens, with periodic cicadas,
is they have what are called stragglers. So the ones we are seeing now are the stragglers
of Brood X and are coming out 4 years early. This is actually fairly well known with
cicadas that they’ll come out a bit earlier than the 17 years. And, it’s usually at
the four-year mark. So, 2017 is exactly when we expect to see some stragglers for
the main emergence that should happen in 2021. This is a mid-Atlantic brood. Brood
X encompasses most of Maryland but goes up into Pennsylvania, New Jersey and [down
to] Virginia. There are about 15 broods emerging around the country.

Why is it happening now?

It’s unclear, but these periodic cicadas have a really strange lifecycle. There’s
several different species that live in the eastern United States. They have either
a 17-year or 13-year cycle. This particular brood that we’re seeing now is one that
has a 17-year cycle. But for reasons that are not entirely clear, it’s been documented
that occasionally we’ll have early emergences, which is what we’re having right now,
typically at the four-year mark. That is what we’re seeing this spring.

What triggers the cicadas to come out in 17 years? How do they keep count?

That part is still a little bit of a mystery in terms of how that works exactly. But
the basic lifecycle is that they’ll emerge, as we see now. And this is about the right
time—usually late May to early June. It’s been really warm this spring, so they’ve
been coming a little earlier in May.

What they do is make these big mass emergences, and what happens is the males will
go up the trees and sing and attract the females, they will mate and the females lay
eggs—typically in the tops of trees. She’ll make a little slit in the tops of branches
and lay usually around 20 eggs, and those eggs will hatch in a few weeks and little
developing “nibs” will fall to the ground. The “nibs” are very tiny—usually about
the size of a grain of rice. They feed on grass roots, and eventually they make their
way to feeding on tree roots. One of the reasons we find them a lot at the edges of
woods is it’s thought it provides access to grass. This is how they begin their lifecycle.
They will live underground for 17 years before they emerge again.

How long is the lifecycle?

Usually by the beginning of July their finished. We’re seeing them now, and they’ll
start singing. I’ve heard a couple on campus just this morning. They’ll go through
mating, and once that happens the adults die. One of the things we won’t get to experience
this year as much is the songs of the species, which is pretty specular. They’re pretty
quiet this year. It doesn’t sound quiet when it’s millions of them emerging, but we
won’t quite get that this year because it’s not the main emergence we’re seeing. You
can hear them, but they’re very faint as they’re singing along.

Could climate change be effecting their lifecycle?

Could the effect of global climate change be affecting them? It’s unclear. One of
the things is that these stragglers commonly come out four years before which is part
of the natural biology which is probably what’s driving some of these different broods
at different years in the first place.

One of the values of having an insect collection, like we have at Towson University,
is it actually provides an historical record so we can look at specimens from decades
ago and see when the emergence occurred and when did we have stragglers. This data
provides an indication of changes that might be afoot. However, scientists would have
to look at the longer timeframe. It’s important to record these records now because
that will provide information to researchers down the line that might give us an idea
if this is because of climate change or something else.

How is social media affecting the research?

One of the things that’s exciting with social media now is we’re probably getting
a much fuller picture of what these stragglers look like in the first place because
it’s easier for people to report it. Whereas, not that long ago, it was tougher for
us to get that data. Were probably getting more information and more precise locations
that we used to get in the past.

This is one of the things we get to experience every 17 years. Scientists have wondered
about these fascinating little creatures, how they evolved and why it is the way it
is. There’s still a lot of questions that researchers are looking to answer about
the periodic cicadas.